There are many instances where it is desirable to transmit data between first and second voltage domains whilst maintaining galvanic isolation between those voltage domains. Examples include power and industrial control systems, motor control systems and healthcare applications. It is generally desirable that such data isolators offer high speed data transmission and good immunity to spurious transmissions. One source of spurious data transmission is common mode noise. In general, avoiding spurious transmissions leads designers towards solutions that reduce data throughput, such as bigger voltage swings across a transformer and bigger separation between detection thresholds in a receiver such that the likelihood that common mode noise at the transmitter being erroneously detected as a data signal at the receiver is reduced.